Exxonmobil Upstream Research Company

Dez Chu

Grant A Gist

The invention is a method for inferring the saturation and pressure change of a reservoir by combining the information from 4D (time-lapse) seismic and time lag data volumes () derived from the 4D seismic, well logs (), and reservoir simulation results (when simulator results are available) and featuring one or more 4D well ties () for a quantitative 4D interpretation. The inventive method uses model-based inversion incorporating rock physics () at well locations (), and is statistical-based () away from wells. The method thus allows integration () of rock physics model and reservoir simulation and honors 4D seismic change.

Inversion of 4D seismic data

Method for deriving a reservoir property change data volume from time shifts used to time-align 4D seismic survey data (). The time alignment is performed on at least one angle stack of 4D data to determine a time-shift data volume (). When multiple angle stacks are used, the time shifts are corrected to zero offset. A running time window is defined, and within each window the time shifts are best fit to a straight-line function of time (depth), one angle stack at a time (). The slopes from the straight line fits from different angle stacks are averaged at each voxel in the data volume, which yields a reservoir properties (&#x394;v/v) data volume (). This data volume may be filtered with a low-pass filter to improve signal-to-noise (). The resulting data volume may be merged with the 4D data volume to expand its bandwidth (), or it may be converted into a reservoir saturation and pressure change data volume () using a rock-physics model ().

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Bellaire, TX, United States of America

Dez Chu